For portable electronic devices, such as cell phones, personal digital assistants, notebook computers, camcorders, and handheld game machines, advanced functionality results in an increased number of heat-generating components mounted on a board. In use of the portable electronic device, heat dissipation from heat-generating components might cause the package surface to be locally heated to high temperature.
Patent Document 1 discloses a structure in which heat from heat-generating components housed in the package of a portable electronic device is advantageously diffused by a heat-conducting member with superior heat dissipation performance which is arranged around the heat-generating components. Examples of the heat-conducting member include metallic materials such as aluminum alloy, magnesium alloy, stainless steel, and plain steel.
Patent Documents 2 to 4 disclose flame-retarded resin compositions being used as materials for packages and components of electronic devices. Specifically, Patent Document 2 discloses a flame-retardant resin composition which includes aromatic polycarbonate having a phosphorous flame retardant added thereto. Patent Document 3 discloses a flame-retardant resin composition which includes polycarbonate having a halogen flame retardant added thereto. Patent Document 4 discloses a flame-retardant resin composition which includes polyphenylene ether having a phosphoric acid ester compound added thereto.
Patent Document 5 discloses a resin composition containing a heat-absorbing material such as aluminum hydroxide or magnesium hydroxide. Aluminum hydroxide and magnesium hydroxide reduce combustion heat by being heated. Also, such an endothermic reaction is a reaction in which water is released. The endothermic reaction as such exerts a flame retardant effect.
Incidentally, secondary batteries, such as lithium-ion secondary batteries and nickel-metal hydride storage batteries, which have high capacity and high energy density, can be readily reduced in size and weight. Accordingly, they are widely used as power sources for portable electronic devices.
Such a secondary battery when it is in abnormal condition could abruptly generate heat due to its high energy density. Such heat generation might abruptly increase the surface temperature of the secondary battery.
Patent Document 6 discloses a battery pack including an exterior case, batteries housed in the exterior case, and a heat-insulating layer formed between the inner surface of the exterior case and the batteries. Patent Document 6 also discloses that such a heat-insulating layer prevents reduction in battery performance due to lowered environmental temperature.
Patent Document 1: International Publication WO2008/062879 pamphlet
Patent Document 2: Specification of Japanese Patent No. 3682148
Patent Document 3: Japanese Laid-Open Patent Publication No. 10-46015
Patent Document 4: Japanese Laid-Open Patent Publication No. 9-82293
Patent Document 5: Specification of Japanese Patent No. 3408676
Patent Document 6: Japanese Laid-Open Patent Publication No. 5-234573